x86/MSI-X: be more careful during teardown

When a device gets detached from a guest, pciback will clear its
command register, thus disabling both memory and I/O decoding. The
disabled memory decoding, however, has an effect on the MSI-X table
accesses the hypervisor does: These won't have the intended effect
anymore. Even worse, for PCIe devices (but not SR-IOV virtual
functions) such accesses may (will?) be treated as Unsupported
Requests, causing respective errors to be surfaced, potentially in the
form of NMIs that may be fatal to the hypervisor or Dom0 is different
ways. Hence rather than carrying out these accesses, we should avoid
them where we can, and use alternative (e.g. PCI config space based)
mechanisms to achieve at least the same effect.

At this time it continues to be unclear whether this is fixing an
actual bug or is rather just working around bogus (but apparently
common) system behavior.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index 78e3f2e845699c544772caeae4214c512945acf6..62fb319ce2896242c3dc9975f10167f450fcbbbb 100644 (file)
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -217,9 +217,9 @@ void destroy_irq(unsigned int irq)
     }
 
     spin_lock_irqsave(&desc->lock, flags);
-    desc->status  |= IRQ_DISABLED;
     desc->status  &= ~IRQ_GUEST;
     desc->handler->shutdown(desc);
+    desc->status |= IRQ_DISABLED;
     action = desc->action;
     desc->action  = NULL;
     desc->msi_desc = NULL;
@@ -995,8 +995,8 @@ void __init release_irq(unsigned int irq, const void *dev_id)
     spin_lock_irqsave(&desc->lock,flags);
     action = desc->action;
     desc->action  = NULL;
-    desc->status |= IRQ_DISABLED;
     desc->handler->shutdown(desc);
+    desc->status |= IRQ_DISABLED;
     spin_unlock_irqrestore(&desc->lock,flags);
 
     /* Wait to make sure it's not being used on another CPU */
@@ -1732,8 +1732,8 @@ static irq_guest_action_t *__pirq_guest_unbind(
     BUG_ON(action->in_flight != 0);
 
     /* Disabling IRQ before releasing the desc_lock avoids an IRQ storm. */
-    desc->status |= IRQ_DISABLED;
     desc->handler->disable(desc);
+    desc->status |= IRQ_DISABLED;
 
     /*
      * Mark any remaining pending EOIs as ready to flush.

diff --git a/xen/arch/x86/msi.c b/xen/arch/x86/msi.c
index 321b6aaf3141c05a91fa51621cb288b77dab502c..dfa93295175f8086bae531a4c690380cee67133d 100644 (file)
--- a/xen/arch/x86/msi.c
+++ b/xen/arch/x86/msi.c
@@ -123,6 +123,27 @@ static void msix_put_fixmap(struct arch_msix *msix, int idx)
     spin_unlock(&msix->table_lock);
 }
 
+static bool_t memory_decoded(const struct pci_dev *dev)
+{
+    u8 bus, slot, func;
+
+    if ( !dev->info.is_virtfn )
+    {
+        bus = dev->bus;
+        slot = PCI_SLOT(dev->devfn);
+        func = PCI_FUNC(dev->devfn);
+    }
+    else
+    {
+        bus = dev->info.physfn.bus;
+        slot = PCI_SLOT(dev->info.physfn.devfn);
+        func = PCI_FUNC(dev->info.physfn.devfn);
+    }
+
+    return !!(pci_conf_read16(dev->seg, bus, slot, func, PCI_COMMAND) &
+              PCI_COMMAND_MEMORY);
+}
+
 /*
  * MSI message composition
  */
@@ -166,7 +187,7 @@ void msi_compose_msg(unsigned vector, const cpumask_t *cpu_mask, struct msi_msg
     }
 }
 
-static void read_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
+static bool_t read_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
 {
     switch ( entry->msi_attrib.type )
     {
@@ -201,6 +222,8 @@ static void read_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
     {
         void __iomem *base = entry->mask_base;
 
+        if ( unlikely(!memory_decoded(entry->dev)) )
+            return 0;
         msg->address_lo = readl(base + PCI_MSIX_ENTRY_LOWER_ADDR_OFFSET);
         msg->address_hi = readl(base + PCI_MSIX_ENTRY_UPPER_ADDR_OFFSET);
         msg->data = readl(base + PCI_MSIX_ENTRY_DATA_OFFSET);
@@ -212,6 +235,8 @@ static void read_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
 
     if ( iommu_intremap )
         iommu_read_msi_from_ire(entry, msg);
+
+    return 1;
 }
 
 static int write_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
@@ -262,6 +287,8 @@ static int write_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
     {
         void __iomem *base = entry->mask_base;
 
+        if ( unlikely(!memory_decoded(entry->dev)) )
+            return -ENXIO;
         writel(msg->address_lo,
                base + PCI_MSIX_ENTRY_LOWER_ADDR_OFFSET);
         writel(msg->address_hi,
@@ -289,7 +316,8 @@ void set_msi_affinity(struct irq_desc *desc, const cpumask_t *mask)
     ASSERT(spin_is_locked(&desc->lock));
 
     memset(&msg, 0, sizeof(msg));
-    read_msi_msg(msi_desc, &msg);
+    if ( !read_msi_msg(msi_desc, &msg) )
+        return;
 
     msg.data &= ~MSI_DATA_VECTOR_MASK;
     msg.data |= MSI_DATA_VECTOR(desc->arch.vector);
@@ -349,23 +377,27 @@ int msi_maskable_irq(const struct msi_desc *entry)
            || entry->msi_attrib.maskbit;
 }
 
-static void msi_set_mask_bit(struct irq_desc *desc, bool_t host, bool_t guest)
+static bool_t msi_set_mask_bit(struct irq_desc *desc, bool_t host, bool_t guest)
 {
     struct msi_desc *entry = desc->msi_desc;
+    struct pci_dev *pdev;
+    u16 seg;
+    u8 bus, slot, func;
     bool_t flag = host || guest;
 
     ASSERT(spin_is_locked(&desc->lock));
     BUG_ON(!entry || !entry->dev);
+    pdev = entry->dev;
+    seg = pdev->seg;
+    bus = pdev->bus;
+    slot = PCI_SLOT(pdev->devfn);
+    func = PCI_FUNC(pdev->devfn);
     switch ( entry->msi_attrib.type )
     {
     case PCI_CAP_ID_MSI:
         if ( entry->msi_attrib.maskbit )
         {
             u32 mask_bits;
-            u16 seg = entry->dev->seg;
-            u8 bus = entry->dev->bus;
-            u8 slot = PCI_SLOT(entry->dev->devfn);
-            u8 func = PCI_FUNC(entry->dev->devfn);
 
             mask_bits = pci_conf_read32(seg, bus, slot, func, entry->msi.mpos);
             mask_bits &= ~((u32)1 << entry->msi_attrib.entry_nr);
@@ -374,25 +406,54 @@ static void msi_set_mask_bit(struct irq_desc *desc, bool_t host, bool_t guest)
         }
         break;
     case PCI_CAP_ID_MSIX:
-    {
-        int offset = PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET;
-        writel(flag, entry->mask_base + offset);
-        readl(entry->mask_base + offset);
-        break;
-    }
+        if ( likely(memory_decoded(pdev)) )
+        {
+            writel(flag, entry->mask_base + PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
+            readl(entry->mask_base + PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
+            break;
+        }
+        if ( flag )
+        {
+            u16 control;
+            domid_t domid = pdev->domain->domain_id;
+
+            pdev->msix->host_maskall = 1;
+            control = pci_conf_read16(seg, bus, slot, func,
+                                      msix_control_reg(entry->msi_attrib.pos));
+            if ( control & PCI_MSIX_FLAGS_MASKALL )
+                break;
+            pci_conf_write16(seg, bus, slot, func,
+                             msix_control_reg(entry->msi_attrib.pos),
+                             control | PCI_MSIX_FLAGS_MASKALL);
+            if ( pdev->msix->warned != domid )
+            {
+                pdev->msix->warned = domid;
+                printk(XENLOG_G_WARNING
+                       "cannot mask IRQ %d: masked MSI-X on Dom%d's %04x:%02x:%02x.%u\n",
+                       desc->irq, domid, pdev->seg, pdev->bus,
+                       PCI_SLOT(pdev->devfn), PCI_FUNC(pdev->devfn));
+            }
+            break;
+        }
+        /* fall through */
     default:
-        BUG();
-        break;
+        return 0;
     }
     entry->msi_attrib.host_masked = host;
     entry->msi_attrib.guest_masked = guest;
+
+    return 1;
 }
 
 static int msi_get_mask_bit(const struct msi_desc *entry)
 {
-    switch (entry->msi_attrib.type) {
+    if ( !entry->dev )
+        return -1;
+
+    switch ( entry->msi_attrib.type )
+    {
     case PCI_CAP_ID_MSI:
-        if (!entry->dev || !entry->msi_attrib.maskbit)
+        if ( !entry->msi_attrib.maskbit )
             break;
         return (pci_conf_read32(entry->dev->seg, entry->dev->bus,
                                 PCI_SLOT(entry->dev->devfn),
@@ -400,6 +461,8 @@ static int msi_get_mask_bit(const struct msi_desc *entry)
                                 entry->msi.mpos) >>
                 entry->msi_attrib.entry_nr) & 1;
     case PCI_CAP_ID_MSIX:
+        if ( unlikely(!memory_decoded(entry->dev)) )
+            break;
         return readl(entry->mask_base + PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET) & 1;
     }
     return -1;
@@ -407,12 +470,16 @@ static int msi_get_mask_bit(const struct msi_desc *entry)
 
 void mask_msi_irq(struct irq_desc *desc)
 {
-    msi_set_mask_bit(desc, 1, desc->msi_desc->msi_attrib.guest_masked);
+    if ( unlikely(!msi_set_mask_bit(desc, 1,
+                                    desc->msi_desc->msi_attrib.guest_masked)) )
+        BUG_ON(!(desc->status & IRQ_DISABLED));
 }
 
 void unmask_msi_irq(struct irq_desc *desc)
 {
-    msi_set_mask_bit(desc, 0, desc->msi_desc->msi_attrib.guest_masked);
+    if ( unlikely(!msi_set_mask_bit(desc, 0,
+                                    desc->msi_desc->msi_attrib.guest_masked)) )
+        WARN();
 }
 
 void guest_mask_msi_irq(struct irq_desc *desc, bool_t mask)
@@ -422,13 +489,15 @@ void guest_mask_msi_irq(struct irq_desc *desc, bool_t mask)
 
 static unsigned int startup_msi_irq(struct irq_desc *desc)
 {
-    msi_set_mask_bit(desc, 0, !!(desc->status & IRQ_GUEST));
+    if ( unlikely(!msi_set_mask_bit(desc, 0, !!(desc->status & IRQ_GUEST))) )
+        WARN();
     return 0;
 }
 
 static void shutdown_msi_irq(struct irq_desc *desc)
 {
-    msi_set_mask_bit(desc, 1, 1);
+    if ( unlikely(!msi_set_mask_bit(desc, 1, 1)) )
+        BUG_ON(!(desc->status & IRQ_DISABLED));
 }
 
 void ack_nonmaskable_msi_irq(struct irq_desc *desc)
@@ -740,6 +809,9 @@ static int msix_capability_init(struct pci_dev *dev,
     control = pci_conf_read16(seg, bus, slot, func, msix_control_reg(pos));
     msix_set_enable(dev, 0);/* Ensure msix is disabled as I set it up */
 
+    if ( unlikely(!memory_decoded(dev)) )
+        return -ENXIO;
+
     if ( desc )
     {
         entry = alloc_msi_entry(1);
@@ -879,7 +951,8 @@ static int msix_capability_init(struct pci_dev *dev,
     ++msix->used_entries;
 
     /* Restore MSI-X enabled bits */
-    pci_conf_write16(seg, bus, slot, func, msix_control_reg(pos), control);
+    pci_conf_write16(seg, bus, slot, func, msix_control_reg(pos),
+                     control & ~PCI_MSIX_FLAGS_MASKALL);
 
     return 0;
 }
@@ -1024,8 +1097,16 @@ static void __pci_disable_msix(struct msi_desc *entry)
 
     BUG_ON(list_empty(&dev->msi_list));
 
-    writel(1, entry->mask_base + PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
-
+    if ( likely(memory_decoded(dev)) )
+        writel(1, entry->mask_base + PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
+    else if ( !(control & PCI_MSIX_FLAGS_MASKALL) )
+    {
+        printk(XENLOG_WARNING
+               "cannot disable IRQ %d: masking MSI-X on %04x:%02x:%02x.%u\n",
+               entry->irq, dev->seg, dev->bus,
+               PCI_SLOT(dev->devfn), PCI_FUNC(dev->devfn));
+        control |= PCI_MSIX_FLAGS_MASKALL;
+    }
     pci_conf_write16(seg, bus, slot, func, msix_control_reg(pos), control);
 
     _pci_cleanup_msix(dev->msix);
@@ -1199,15 +1280,24 @@ int pci_restore_msi_state(struct pci_dev *pdev)
             nr = entry->msi.nvec;
         }
         else if ( entry->msi_attrib.type == PCI_CAP_ID_MSIX )
+        {
             msix_set_enable(pdev, 0);
+            if ( unlikely(!memory_decoded(pdev)) )
+            {
+                spin_unlock_irqrestore(&desc->lock, flags);
+                return -ENXIO;
+            }
+        }
 
         msg = entry->msg;
         write_msi_msg(entry, &msg);
 
         for ( i = 0; ; )
         {
-            msi_set_mask_bit(desc, entry[i].msi_attrib.host_masked,
-                             entry[i].msi_attrib.guest_masked);
+            if ( unlikely(!msi_set_mask_bit(desc,
+                                            entry[i].msi_attrib.host_masked,
+                                            entry[i].msi_attrib.guest_masked)) )
+                BUG();
 
             if ( !--nr )
                 break;